Machine tools utilizing a cutting or abrasive tool are commonly used in a wide variety of manufacturing endeavors. A commonly used machine tool utilizes a rotating cutting tool having a number of sharp edges, and it performs its cutting function by rapidly cutting small particles from the workpiece. Another variety of rotating machine tool utilizes a tool having an abrasive surface that rotates or reciprocates to abrade a surface of the workpiece.
The collection of particles or "chips" produced by cutting tools and the collection of dust produced by abrasive tools has long posed a serious problem. Chips can be thrown from the cutting tool at a high velocity and thus injure the machine tool operator, particularly if he or she is not wearing eye protectors. Smaller chips from cutting tools and dust from abrasive machine tools can be inhaled by the operator thus potentially causing respiratory health problems. Furthermore, chips and dust, if not collected, can clutter up the working environment thus making the floors and work surfaces unsightly and slippery, and they can find their way into the bearings of rotating machinery and other precision devices thus potentially causing severe damage.
More recently still another dust and chip collection problem has arisen in the use of machine tools for machining composite materials, such as graphite-epoxy and the like, primarily for the aircraft industry. Machining such composite materials generates a large amount of chips and particles which are electrically conductive since they contain a great deal of graphite. The graphite chips and dust have a tendency to find their way into such electrical components as, for example, computer control terminals used to operate the machine tool. Thus, the problem of effectively collecting chips and dust produced by machine tools has recently become even more acute.
A number of devices have been developed in an attempt to collect dust and chips generated by machine tools. Although some of these devices are somewhat effective in collecting some types of dust and chips, none of these devices are adequately effective in collecting virtually all types of dust and chips, including dust and chips produced by machining composite materials.
One conventional device for collecting chips and dust produced by rotating machine tools utilizes a vacuum drawing air through a duct having an inlet positioned adjacent the machine tool. However, these conventional vacuum systems are not capable of collecting a sufficiently large percentage of the dust and particles for a number of reasons. First, it is difficult to make the vacuum air stream surround the cutting or abrasive tool from all sides. As a result, a significant amount of chips and dust can escape from areas in which the vacuum air stream is relatively slow. Second, the velocity of the vacuum air stream is generally not sufficiently high to counteract the sometimes very high outwardly directed velocity of chips and dust. As a result, high velocity chips and dust can often escape from vacuum collection systems.
One approach that has been taken to solve the above described limitations of conventional vacuum collection systems has been to surround the machine tool with a shroud. In theory, the shroud directs the vacuum air stream around the machine tool, and it also increases the velocity of the air stream adjacent the machine tool. However, for such shrouds to be effective, they must surround the cutting tool very closely and must also be positioned very close to the workpiece so that the gap between the lower edge of the shroud and the workpiece is very small. Shrouds that closely surround the cutting tool and are positioned very close to the workpiece have a tendency to obstruct the machine tool operator's view of the tool and workpiece, and can interfere with the movement of the workpiece, particularly when ribs, protrusions or the like extend upwardly from the upper surface of the workpiece.
Another conventional approach to collecting dust and chips has been to position air nozzles adjacent the cutting tool and direct an air stream from the nozzle toward the cutting tool. In fact, U.S. Pat. No. 4,011,792 to Davis discloses the use of such nozzles with a vacuum system using a shroud as described above. The air streams generated by these air nozzles may be effective in removing chips, shavings and the like from the machine tool and/or workpiece. However, these prior art air nozzle devices, whether used alone or with a vacuum shroud, do not contribute significantly to the collection of the chips and shavings. The air streams generated by these air nozzles impact on the machine tool from only a limited number of directions. Thus, while air streams may prevent dust and chips from escaping toward the nozzles, they do not prevent, and may even contribute to, the escape of dust and chips in other directions.
The prior art thus not only fails to recognize the limitations of these conventional approaches to collecting dust and chips, but it also fails to teach of any structure that is capable of effectively collecting virtually all types of dust and chips in a manner that does not intefere with the operation of machine tools.